Java Programming with Oracle JDBC

Servlet Connection Strategies

From a programmer’s perspective, a servlet has three stages to its life cycle. They are defined by the following three methods, or types of methods:

init( )

This method is normally used to perform any initialization that should take place only once in the lifetime of the servlet. The init( ) method is invoked automatically before any of the servlet’s doXXX( ) methods can be called.

doXXX( )

The various do methods -- doGet( ), doDelete( ), doPost( ), and doPut( ) -- are called as needed by web users to satisfy their dynamic content and form processing needs.

destroy( )

This method is called just before the servlet container removes the servlet from memory, which typically happens when the servlet container itself is shutting down.

Given the life cycle described here, you have four strategies for making a database connection. The differences between these strategies hinge on when the connection is made and on whether connections are shared between servlets. The four strategies are:

Per-transaction connection

You load the Oracle JDBC driver in the servlet’s init( ) method, open a connection at the beginning of each doXXX( ) method, and close that connection at the end of each doXXX( ) method.

Dedicated connection

You use a combination of the init( ) and destroy( ) methods, whereby you load the driver and open a connection in the init( ) method, and then close that connection in the destroy( ) method. As a result, the servlet uses one connection that remains ...